Seattle Ride the Ducks crash
Investigators are pictured at the scene of a crash between a Ride the Ducks vehicle and a charter bus on the Aurora Bridge in Seattle, Washington September 24, 2015. Local media reported four dead and 12 critically injured.REUTERS/Jason Redmond

At least four people have died and a dozen others have been critically injured after a charter bus and amphibious "Ride the Ducks" vehicle collided in Seattle, Washington on Thursday (24 September). Footage and photographs from the scene showed the side of the bus had been ripped open from the force of the collision on Seattle's Aurora bridge.

The four people killed and the people with the most severe injuries were on board the bus, the city's fire department said. It evaluated about 50 people after the crash, which also left 20 people with non-life threatening injuries.

"We've had a terrible tragedy," Seattle's mayor, Ed Murray told a press conference. "There's been a terrible loss of life. The thoughts of this city go out to everyone."

After speaking with hospital and North Seattle College officials, a representative of the Chinese consulate confirmed that all four bus passengers who died were students. Ron Chow told the Seattle Times that 48 students from six countries were involved in the crash, but he was unsure how many of them are Chinese.

Two smaller passenger vehicles were also involved in the crash, which happened at about 11.00 local time (18.00 GMT). A witness said they saw the duck boat lurch suddenly, losing its front wheel before clipping a sports utility vehicle and colliding with the bus, which was traveling in the opposite direction.

Witness Brad Volm, whose SUV was involved in a crash with another vehicle that swerved to avoid the main crash, told the Seattle Times: "It all happened so fast. I got out of my car and there were bodies just everywhere. People laying in the street."

Many of the "Ride the Ducks" boats, which can drive on roads and float on water, were originally built as World War II landing craft. There are thought to be up to 1,000 in operation around the world. However, duck boats have been described as "death traps" in the US following a number of fatalities involving the crafts.

In 2010, two members of a Hungarian tour group were killed following an engine fire that disabled a Ride the Ducks amphibious bus on Philadelphia's Delaware River. In 2013, a group of tourists in London were rescued from the River Thames after a Duck Tours boat caught fire.